NEW YORK, United States — Tiffany & Co. couldn’t persuade enough customers to put a little blue box under the tree this holiday season.

After a sluggish November and December — when sales fell 1 percent — the luxury jewelry chain cut its annual forecast today. The move jolted investors, who had expected the company to benefit more from an expanding U.S. economy, and sent the shares down as much as 15 percent. That was the biggest intraday drop since the week following the Sept. 11, 2001, terror attacks.

The retailer is suffering from a slump in Japan and a strengthening dollar, which has eroded overseas sales and made it less appealing for tourists visiting the U.S. to buy Tiffany products. But a decline in the company’s home region was the biggest surprise.

“The shocking thing was how slow the Americas was,” said Dorothy Lakner, an analyst at Topeka Capital Markets in New York. “Given the strength in the economy, given the strength in the stock market, it was setting them up for a really good holiday season.”

The stock closed at $89.01 today in New York, erasing the gain from last year. As Tiffany — and its investors — look for a rebound in 2015, here are four of the biggest challenges.

GETTING AMERICANS TO SPEND

The Americas make up about 49 percent of Tiffany’s sales, and improving economic conditions seemed poised to lift Tiffany’s sales. The company had raised its prices to pad margins and stepped up its marketing — efforts that had shown payoff in previous quarters. The trend came to a halt this holiday season, when sales in its home region fell 1 percent to $544 million, compared with an increase of 6 percent a year earlier.

Most other luxury companies haven’t reported results yet from the holidays, but Americans overall have shifted more spending toward discount chains. Mass merchants and supermarkets were some of the big winners from the holidays, with department stores and clothing retailers suffering, according to payment- technology firm First Data.

Many Americans still have a frugal mindset in the wake of the last recession, and that may be hampering Tiffany’s ability to push beyond its well-heeled customer base.

CURRENCY WOES

The dollar’s gains against the euro, yen and other currencies took a toll on Tiffany’s results over the holidays. Currency conversions turned 4 percent same-store growth in Europe into a 1 percent gain, and it made Japan’s already-bleak 8 percent decline into a 16 percent plunge.

While Tiffany isn’t alone in struggling with currency fluctuations, the chain gets the majority of its sales from overseas, leaving it especially exposed. Another high-profile victim: Apple Inc., which last week increased the prices of software applications sold overseas to compensate for the stronger dollar.

For Tiffany, the trend also could be cutting into its foreign-tourism business. With the dollar so strong, visitors from other countries might be less willing to make a trip to New York to buy a pendant at Tiffany’s flagship store.

TIFFANY T

Design Director Francesca Amfitheatrof debuted her first collection, Tiffany T, last year. In its advertisements, Tiffany highlighted the high-margin fashion jewelry items, characterized by their lack of gemstones. The products — priced from a few hundred dollars to $20,000 — were designed to change the way jewelery is purchased. They target women who want to buy gifts for themselves, rather than appealing to men shopping for their wives or girlfriends.

While Tiffany said the collection sold well, it fell short in one key area: creating a halo effect for other products.

“Tiffany T drove solid growth in fashion gold jewelry, but same momentum did not carry through to other jewelry categories as anticipated,” Oliver Chen, an analyst at Cowen & Co. in New York, said in a report.

MAKING THE MOST OF ASIA

Japanese consumers have long represented once of the most vital markets for any luxury retailer. But the country has fallen back into recession following sales-tax increases, and it’s struggling with an aging population.

That’s troubling for Tiffany, which has almost a fifth of its stores in the country. The company blamed its Japanese woes on “weak economic conditions affecting consumer spending.”

The good news is the rest of the region isn’t suffering from the same malaise. Growth in China and Singapore helped propel Asia-Pacific by 7 percent in the period, rising to $210 million in U.S. dollars.